For Verizon, VoLTE means video calls, HD voice and Alaska

High-definition voice calls are now available on all four major U.S. carriers after a nationwide launch by Verizon on Tuesday, though there's a long way to go before all those systems all work together and run over LTE.

Verizon Wireless subscribers with the right handsets will be able to start making high-definition voice and video calls over the carrier's LTE network in the next few weeks, kicking off a long-awaited transition that eventually will eliminate Verizon's traditional cellular technology.

VoLTE, or voice over LTE, will offer quicker call setup, make voice conversations sound better and let users jump into a video chat just by tapping a button on the screen, Verizon says. But those high-fidelity calls will drop if you leave the LTE coverage area, and last week Verizon wasn't ready to say which phones will be ready to use the service when it launches.

VoLTE turns phone calls into packets and sends them over the same network that carries data from apps and the Web. It's a more efficient way for mobile operators to deliver voice service and lets them devote more bandwidth to calls, allowing for higher quality sound: seven octaves, versus just four on circuit-switched 3G networks, according to Verizon.

In the demonstration last week, which Verizon said was over its commercial LTE network, VoLTE calls were distinctly clearer and the video calls had fairly good quality and video-to-voice synchronization.

With VoLTE on, subscribers will be able to make and receive VoLTE calls using regular phone numbers between any two Verizon phones that have the software activated. Part of the new technology is a presence feature that indicates on the contact list which people currently have VoLTE capability. A call with anyone else, or one that you start outside the LTE coverage area, will only have CDMA quality. And even though they're made up of data packets, the new HD voice and video calls won't work over Wi-Fi.

There's one shortcoming that could trip up Verizon VoLTE users: If a call starts on LTE and one participant goes out of the LTE coverage area into 3G-only territory, the call will drop and have to be restarted. At least one other carrier, T-Mobile, says it has solved that problem on its own network using a recent addition to the LTE standard.

Starting up Verizon's new service won't cost subscribers anything, but the packet-based voice calls will count against their minutes if they have time-limited plans, and the video part of the calls will count as data use. For a subscriber who finds they like upgrading voice calls to video chats, the extra bytes could add up.

Some might say Verizon ought to give its customers a break on those calls, because shifting voice off the older CDMA network should eventually save the carrier money. For the last four years, Verizon has had to maintain two networks, one being the 3G CDMA system that switches calls using old-fashioned circuits and the other being the more modern LTE infrastructure. LTE is typically faster for subscribers but also better for carriers. It's a pure IP (Internet Protocol) packet network, and it uses carriers' pricey licensed frequencies more efficiently than CDMA.

All the major U.S. carriers are expected to use the same standard for VoLTE and work together to make sure customers can make VoLTE calls to their friends who use other service providers. But the migration will take several years. T-Mobile and AT&T have introduced VoLTE in parts of their coverage areas. Sprint offers HD Voice service today over 3G, but hasn't said when it will introduce VoLTE. Verizon is the first carrier to switch on VoLTE across its entire LTE footprint.

Even at Verizon, the technology will be rolled out in several steps.

First, Verizon needs to make VoLTE work on the phones that its own subscribers are already using. Last week, the company demonstrated the new feature on an LG G2 smartphone and said it will also be available on several smartphones around launch time, but it wouldn't name those devices. The first batch of phones will graduate to VoLTE through over-the-air software upgrades, and their owners will get to choose whether to activate VoLTE.

Starting in 2016, Verizon expects to start shipping some phones that rely solely on LTE for voice calling. Over time, the carrier will fill in its 3G-only areas with LTE coverage until the last 3G cells are turned off, but that won't be until at least 2020, the company says. By then, all the handsets it sells should be VoLTE-only.

In Alaska, Verizon's getting a head start on LTE-only service. It's selling mobile voice service for the first time in the state thanks to the VoLTE launch. Verizon turned on an LTE network and launched data services in the most populated areas of Alaska last year. It won't build a 3G network there at all, instead relying on roaming partners for additional coverage.

In time, Verizon also hopes to add more IP-based services, such as text chatting and file transfers. There's a whole portfolio of standard communications technologies, called RCS (Rich Communications Services), that might help carriers offer alternatives to features already delivered by so-called over-the-top Internet providers such as Google and Skype. The advertised advantage of RCS, and of Verizon's new VoLTE voice and video calls is that they are more tightly integrated with the carrier's network and user interface.

However, RCS appears to be an over-engineered response to services from Internet companies that already had a long head start, Tolaga's Marshall said. "I don't see them competing at the bleeding edge, by a long shot," he said.

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